This application incorporates by reference Taiwanese application Serial No. 90109220, filed Apr., 17, 2001.
1. Field of the Invention
The invention relates in general to a method of performing printhead maintenance, and more particularly to a maintenance method for increasing the utility of ink used in various inkjet printing apparatus, such as the printer, facsimile machine, and multi-function peripheral (MFP).
2. Description of the Related Art
In the present age of high technology, the computer is a daily necessity for the modern person. Consequently, a variety of associated electronic products (such as scanners, printers, digital cameras, etc.) become highly desirable, the printer being the most popular product. The printer is used to print out the desired information, including documents and colored pictures. The pictures, usually downloaded from the Internet or photographed by the digital camera, are saved on the computer in digital forms and then printed out by the printers. For general printing purposes, the color inkjet printer is still the favorite for home use, considering the printing quality and price.
In the inkjet printer, the ink cartridge is driven right and left, and ink droplets are ejected from the cartridge chamber onto the receiving print material at the appropriate time, and thus the text or picture is formed. According to the liquid droplet ejection system, cartridges of commercially available inkjet printers are generally classified into two typesxe2x80x94bubble (thermal) jet cartridge and piezoelectric cartridge. In present day usage, ink ejection by a thermally driven bubble is the most successful and common, due to its relative simplicity, image quality, and low cost. The bubble jet cartridge mainly comprises heaters, ink, and orifices. The heater activates the ink and generates bubbles, and then the ink is pressurized by the expanding bubbles and ejected through each orifice to print a dot of ink onto a recording medium, such as a sheet of paper. It is critical to control the concentration of ink and the falling location of each droplet during printing, wherein numerous dots of ink combine to form the desired letters or pictures.
However, in some situations, the ink is not ejected smoothly from the orifices, resulting in reduced printing quality. There are several causes of poor-quality ejection. For example, when the ink cartridge is just replaced, the original ink remaining in the orifices may have deteriorated due to a prolonged quiescent period or time-consuming replacement period. Also, ink components accumulated in the orifices could block the flow of ink after operating several printing cycles. In addition, the inkjet printer is typically maintained in the stand-by or quiescent mode, which can stretch over a relatively long interval, sometimes on the order of minutes or even hours. During these quiescent intervals, the ink is allowed to stand and thicken due to evaporation of ink components, and the ink could possibly accumulate in the orifices of the printhead. If the printing effect of an inkjet printer is in doubt, the printer can be commanded to run a print test and print out a predetermined test graph. According to the result of printing the test graph, it can be determined if the maintenance function is required for cleaning the printhead.
In commercially available inkjet printers, the maintenance function is commonly accomplished by brushing, wiping, spraying, vacuum suction, or spitting of ink through the orifice. However, when conventional inkjet printers perform the spitting maintenance, the user does not know which orifices are clogged since the ink is ejected through all orifices, clogged or not. The circuit of the printhead can be controlled to purge only the clogged orifices, so in the conventional maintenance method, the extra ink ejected through the unclogged orifices goes to waste. Details of a conventional maintenance procedure are illustrated below, with reference to FIGS. 1A, 1B, and 2.
FIG. 1A depicts a predetermined test graph of a conventional inkjet printer. An ink cartridge containing four primary colors is taken for illustration. The predetermined test graph 100 is composed of a yellow (Y) test region 110, a magenta (M) test region 120, a cyan (C) test region 130, and a black (K) test region 140. Each test region contains a number of discontinuous linear sections, as shown in FIG. 1A. If none of the orifices is clogged, the printing result of printing the test graph will be identical with the predetermined test graph 100 of FIG. 1A, wherein every single section in the test region is clearly and completely printed.
FIG. 1B illustrates a bad result of printing the test graph of FIG. 1A. Since many orifices of the printhead are clogged, the lines associated with the clogged orifices are not fully represented in the printing result. Thus the printing result 100xe2x80x2 is an incomplete representation of the predetermined test graph 100. According to the foregoing description, the conventional method of determining if the orifices are clogged is to obtain a printing result of the predetermined test graph and examine the result with the naked eye. If the orifices are judged to be clogged, then the printhead receives a maintenance procedure for purging the clogged orifices, upon the user""s request.
FIG. 2 shows a flow chart of a conventional method of performing printhead maintenance. When the orifices seem to be clogged, the user gives a maintenance order to the printer to print out the predetermined test graph (step 204). Then the printing result is obtained and examined to determine whether the orifices are blocked or not (step 206). If the determination is negative (no-clog situation), the orifice inspection is terminated. If the determination is positive (clogged situation), the operation is led to step 208 and all printhead orifices are requested to eject ink continuously. Then steps 204 and 206 are repeated. The maintenance loop of FIG. 2 can be performed repeatedly until all orifices are completely unclogged.
According to the aforementioned illustration, the conventional method of performing printhead maintenance is to make every orifice eject ink continuously so as to purge the clogged orifices. However, this maintenance method does not distinguish between clogged and not clogged orifices, and thus, ink is wastefully consumed in unnecessarily purging the unclogged orifices. The more ink the printhead ejects unnecessarily, the more ink and money the user wastes.
It is therefore an object of the invention to provide a method of performing printhead maintenance, wherein only the orifice group containing clogged orifices is treated by the cleaning action, so that unnecessary consumption of ink is greatly reduced.
According to the objective of the invention, a method of performing printhead maintenance is provided, and comprises the following steps. First, all orifices of the printhead are grouped to form a plurality of orifice groups. Then, a test graph is constructed based on the orifice groups, in order to determine if the orifice groups need to be cleaned. During the construction of the test graph, each test line or curve of the test graph is specifically associated with an orifice group. Therefore, the orifice group containing clogged orifices is revealed after examining the test lines or curves in the printing result of the test graph. If the orifices seem to be clogged, a print test order is sent to the inkjet printer for printing out the test graph. After the printing result is obtained, it is examined with the unaided (naked) eye or with a sensor to see if the printing result completely and clearly represents all orifice groups, and to determine whether the orifices are blocked or not. If the test curves of the printing result are not complete, the orifice groups to be cleaned are selected and a cleaning action, such as ejecting ink through the orifices or wiping the orifices, is run. The maintenance loop can be performed repeatedly until all of the orifices are completely cleaned.